The precipitation in annealing and its effect on permittivity of Fe–Si–Al powders

Abstract SEM images show that some precipitates distributed on the surface of as-annealed Fe–Si–Al powders. Subsequent experimental results indicate that both morphology and microstructure of as-annealed Fe–Si–Al powders change with increasing annealing temperature. Meanwhile, dielectric properties analysis suggesting that both real part e ′ and imaginary part e ″ of the Fe–Si–Al powders decrease significantly after annealed at 450 °C or higher temperature. We assume that it’s the precipitates with low electrical conductivity developed on the surface of powders that increase the surface resistivity of as-annealed powders and leading to a lower imagine part of permittivity. The drop of real part e ′ ascribed to the weakened interfacial polarization which resulted from the decrease of structural defects such as grain boundaries and interfaces during annealing process.